Various techniques are known to interconnect a thick film substrate formed of materials such as alumina or beryllia to an electrical circuit. In particular, various techniques are known to connect a thick film substrate, mounted in a molded plastic housing, through the housing to additional electrical circuitry.
For example, referring to FIGS. 3 and 4, a terminal 90 extends through a housing 91. A ribbon or wire 92 with a solderable surface can be attached using solder 94 to a thick film substrate 93 and soldered or welded to terminal 90 at a portion extending beyond housing 91. The ribbon can be made of a nickel material.
Instead of having a direct connection to a pad on the thick film substrate an "anvil" 95 (FIGS. 1 and 2) can be attached to the pad of thick film substrate 93 and serve as the base for connection to a wire 96. Thus, a weld anvil 95 is soldered to substrate 93 and wire or strap 96 is welded to anvil 95 and welded to housing terminals 90. Wire made of copper is suitable for welding to the anvil and welding to the housing terminal.
Each of these known techniques has numerous manufacturing steps which add to cost and may affect reliability. It would be desirable to eliminate some of the manufacturing steps and eliminate some of the interconnect components required. These are some of the problems this invention overcomes.
FIG. 9 shows the prior art terminal connection of FIGS. 3 and 4 mounted in a housing. A gel 97 covers substrate 93 up to a height above terminal 90. In fact, the interior tip of terminal 90 is bent down from the position shown in FIG. 3 so that the depth of gel 97 can be reduced. It would be desirable to reduce further the depth of the gel.
Housing 91 is typically mounted so that a ground connection is contacted by bottom plate 80. To achieve a connection from plate 80 to a contact on substrate 93 an electrically conductive spacer 81 extends between plate 80 and a terminal 82. An electrically conductive ribbon 83 is coupled between terminal 82 and a connection pad on substrate 93. Spacer 81 is sufficiently rigid mechanically so that a mounting screw pressing terminal 82 toward plate 80 does not cause housing 91 adjacent to spacer 81 to cold flow or deform. Typically, spacer 81 is metal and housing 91 is plastic. It would be desirable to eliminate the need for this spacer.